JS深拷贝的五种方法

1、JSON方法实现

//_tmp和result是相互独立的，没有任何联系，有各自的存储空间。
let deepClone = function (obj) {
    let _tmp = JSON.stringify(obj);//将对象转换为json字符串形式
    let result = JSON.parse(_tmp);//将转换而来的字符串转换为原生js对象
    return result;
};
 
let obj1 = {
    weiqiujaun: {
        age: 20,
        class: 1502
    },
    liuxiaotian: {
        age: 21,
        class: 1501
    }
};
 
let test = deepClone(obj1);
console.log(test);
 // JSON对象实现深拷贝的一些问题 
  //  *无法实现对对象中方法的深拷贝

2、用for…in实现遍历和复制

function deepClone(obj) {
    let result = typeof  obj.splice === "function" ? [] : {};
    if (obj && typeof obj === 'object') {
        for (let key in obj) {
            if (obj[key] && typeof obj[key] === 'object') {
                result[key] = deepClone(obj[key]);//如果对象的属性值为object的时候，递归调用deepClone,即在吧某个值对象复制一份到新的对象的对应值中。
            } else {
                result[key] = obj[key];//如果对象的属性值不为object的时候，直接复制参数对象的每一个键值到新的对象对应的键值对中。
            }
 
        }
        return result;
    }
    return obj;
}
 
let testArray = ["a", "b", "c", "d"];
let testRes = deepClone(testArray);
console.log(testRes);
console.log(typeof testRes[1]);
 
let testObj = {
    name: "weiqiujuan",
    sex: "girl",
    age: 22,
    favorite: "play",
    family: {brother: "son", mother: "haha", father: "heihei"}
};
let testRes2 = deepClone(testObj);
testRes2.family.brother = "weibo";
console.log(testRes2);

3. 使用递归的方式实现深拷贝

 //使用递归的方式实现数组、对象的深拷贝
    function deepClone1(obj) {
      //判断拷贝的要进行深拷贝的是数组还是对象，是数组的话进行数组拷贝，对象的话进行对象拷贝
      var objClone = Array.isArray(obj) ? [] : {};
      //进行深拷贝的不能为空，并且是对象或者是
      if (obj && typeof obj === "object") {
        for (key in obj) {
          if (obj.hasOwnProperty(key)) {
            if (obj[key] && typeof obj[key] === "object") {
              objClone[key] = deepClone1(obj[key]);
            } else {
              objClone[key] = obj[key];
            }
          }
        }
      }
      return objClone;
    }
  let arr = { a: "1", b: "2", c: "3" };
  let arrs = deepClone1(arr)//可以替换成arr看有什么区别
  arr.a = "8";
  console.log(arr)
  console.log(arrs)

4、利用数组的Array.prototype.forEach进copy

let deepClone = function (obj) {
    let copy = Object.create(Object.getPrototypeOf(obj));
    let propNames = Object.getOwnPropertyNames(obj);
    propNames.forEach(function (items) {
        let item = Object.getOwnPropertyDescriptor(obj, items);
        Object.defineProperty(copy, items, item);
 
    });
    return copy;
};
 
let testObj = {
    name: "weiqiujuan",
    sex: "girl",
    age: 22,
    favorite: "play",
    family: {brother: "wei", mother: "haha", father: "heihei"}
}
let testRes2 = deepClone(testObj);
console.log(testRes2);

5. 通过jQuery的extend方法实现深拷贝

 <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.1/jquery.js"></script>
 //记得上一句引入jq
var array = [1,2,3,4];
    var newArray = $.extend(true,[],array);